The drowning of the Tryweryn Valley in the 1960s, despite huge protests, so water could be supplied to Liverpool, came to symbolise the powerlessness of Wales as a nation.

Many people, including Dafydd Wigley, were inspired to become lifelong campaigners for Welsh home rule.

Now, with the Brexit vote unsettling the established order, Plaid Cymru is tentatively exploring the possibility of Welsh independence sooner rather than later.

The trouble is the £15bn funding gap – identified by Cardiff University’s Wales Governance Centre – between what Wales raises in tax and what is spent on public services and welfare payments, mostly pensions.

There are those in Plaid who consider such calculations skewed, and effectively a Unionist plot.

Gwyn Hopkins, a Plaid county councillor in Carmarthenshire, argues that the transfer of resources like water from Wales to England are not included.

Could water, then, prove to be Wales’ economic saviour and make independence affordable?

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There’s a belief that taking charge of our water resources and charging England a market price for it would bring in very large sums. Unfortunately, the position isn’t as simple as that.

Firstly, we no longer live in a country where the water infrastructure is owned by the state.

The industry was privatised in England and Wales in 1989, although the areas served by Welsh Water come under Glas Cymru, a non-for- dividend company funded entirely by bonds, borrowings and income from customers.

Welsh Water is paid to deliver services by Glas Cymru, which at the time of the latest accounts in March 2015 had assets worth £4.4bn.

Buying Glas Cymru for an independent Welsh state would be an expensive outlay, especially at a time when the Cabinet was busy negotiating a bail-out with the International Monetary Fund so those entitled to state pensions could be paid.

Historically, water transfer has not been progressed as, unlike gas and electricity, it would be technically very difficult and extremely expensive to pipe and pump large volumes of water from Wales to other parts of the UK, due to the need for capital investment, topography and electricity costs.

Water is very heavy, so moving it over large distances would involve expensive and energy intensive engineering works.

The environment of Wales benefits from higher than average rainfall than in many other parts of the UK. However, we do not currently have excess water resources in Wales, especially during dry summers.

Most of the rainfall received is retained by the natural environment, rather than being captured and used for public water supply. Our water resources are mainly reservoirs and rivers – we have very little groundwater resources.

To progress water transfers would therefore require major investment in new storage within Wales.

Pontsticill Reservoir overflow (Image: Barrie McConnell)

Another problem is that Glas Cymru’s operational boundaries are not coterminous with geographical boundaries.

The boundaries for water are based on river basins, resulting in Severn Trent serving a large proportion of customers in Mid Wales.

Glas Cymru’s operating area shares a land border with Severn Trent Water and Dee Valley Water, and a water border with Bristol Water - the River Severn estuary - and United Utilities Water - the River Dee estuary.

As the operating company for Glas Cymru, Welsh Water has more than 20 bulk water trades already in place with some of these companies.

The most significant of these by volume is the Elan Valley bulk supply to Severn Trent Water, where Welsh Water exports more than 100,000 megalitres per year to Severn Trent, for it to supply its customers in Birmingham.

To put such a transfer in context, Welsh Water supplies on average around 800 megalitres per day to its own customers.

Welsh Water is Wales’ fifth biggest company in terms of revenue. With its not-for- profit operating model, it is unique in the water industry.

Pontsticill reservoir (Image: Anthony Pritchard)

Most other water companies in England and Wales are owned by foreign investors. For example, Thames’ owners include investors from Australia, Canada, Britain, China and Abu Dhabi.

As things stand, Welsh Water contributes around £1bn a year to the Welsh economy.

It directly employs 3,000 people and supports another 3,400 jobs across the area it serves. The company provides more than three million people across much of Wales, Herefordshire and Deeside with water and wastewater services – the most essential of public services.

It has an extensive network of assets across the area it serves and it would cost around £26bn if itneeded to build them from scratch today.

They include 27,000km of water mains, 65 water treatment works, 92 reservoirs as well as 30,000km of sewer pipes and nearly 900 sewage treatment works.

It invests around £1m a day in its network.

Pipes carrying essential utilities such as water, gas, power and communications

This level of investment - £1.5bn between 2015 and 2020 - is needed given the topography in Wales, and means the company has more assets per head than many other water companies and also the second longest coast line in the industry.

It’s very doubtful whether simply transferring existing water assets to an independent Welsh state could produce more benefit for the Welsh economy.

There is, however, the possibility for water to do more.

The Scottish Government has ambitious plans to turn Scotland into a “Hydro Nation”, using Scottish expertise “to maximise the economic benefit of our abundant water resources within a sound ecological context by reducing energy use, improving efficiency and creating a low carbon water nation”.

There is also a plan to create a water centre of expertise and research with international reach.

The Welsh Government has published A Water Strategy for Wales which sets out the need to prepare for hotter weather as a result of climate change and to cope with a rising population.

At the same time it points out the real potential for economic benefits arising out of water-related activities.

So while the idea of selling water to England may be unrealistic, there are other ways of making money from the most elemental of natural resources.